Administrators appreciate the ability to reconfigure systems to adapt to changes in policy or available resources. In parallel file systems, the mapping from a file reference to its location on devices can help or hinder reconfiguration of the file system.
In PVFS2 file data is split into datafiles. Each datafile has its own reference, and clients identify the server that owns a datafile by checking a table loaded at configuration time. A server can be added to the system by allocating a new range of references to that server and restarting clients with an update table. Likewise, servers can be removed by first stopping clients, next moving datafiles off the server, then restarting with a new table. It is not difficult to imagine providing this functionality while the system is running, and we will be investigating this possibility once basic functionality is stable.